ci: add HOL skill-publish validate workflow

[internet-dot]

I opened this as a small validate-only check for the skill metadata in the repo.

A couple of repo-specific details I checked first:

• GitHub's official MCP Server
• Issue & PR Automation: Create, update, and manage issues and pull requests. Let AI help triage bugs, review code changes, and maintain project boards
• CI/CD & Workflow Intelligence: Monitor GitHub Actions workflow runs, analyze build failures, manage releases, and get insights into your development pipeline

This adds one workflow for . and leaves the runtime code alone.
It only runs the schema and trust checks for the skill metadata in validate mode.

If you would rather place the workflow under a different filename or point it at a different skill directory, I can adjust the branch.